1. Field of the Invention
The present invention relates to a printing-unit cylinder for a rotary printing machine. More particularly, the present invention relates to a transfer cylinder, a plate cylinder or a back pressure cylinder. The present invention further relates to a barrel, a body and an entire printing unit cylinder for effectively dissipating undesired heat during the printing process.
2. Description of the Related Art
When using a transfer cylinder in a rotary printing machine, flexure work in the rubber blanket during rolling contact with a plate cylinder and a back-pressure cylinder produces dissipation energy and results in undesirable heating of the rubber blanket. EP 0 697 284.A1 suggests a solution to the problem by providing internal cooling. However, this internal cooling system is complex and can cause problems in both producing the system and in operating it.
DE 196 19 655 A1 suggests an improvement in heat transfer between the rubber blanket and the transfer cylinder bearing the blanket. It is proposed that the rubber blanket contain a heat-dissipating inlay or underlay designed to dissipate the heat radially to the transfer cylinder. However, in this system localized differences in heating of the blanket still occur. These local temperature differences can be caused by the subject or as a result of the blanket having variations in compressibility. These variations may be caused by a lack of a homogenous blanket material. As a result, the differences in heating over the blanket are transmitted to the transfer cylinder which then has variations in temperature. Non-uniform heating of the transfer cylinder can in turn lead to deformation such as curvature of its longitudinal axis with resultant disruption of ink transfer. This impairs the printing quality.
Non-uniform heating as discussed may also occur on other printing-unit cylinders, for example plate cylinders. The same cylinder deformations and impairment to the printing quality can occur in this instance as well.